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Your timing tab appears to be identical to my '70, so it should be correct for your engine.
My balancer failed several years ago, with some investigation, I discovered that the ZZ4 engine balancer was the same, so installed that one.
Using the piston stop method, my tab and balancer mark are off about 1 degree.
That is acceptable.
Keep in mind when a piston is truly at TDC, the crank can be turned a few degrees in either direction,
BEFORE the piston even thinks about moving downward.
1. I was definitely using the piston stop in the #1 spark plug (front plug nearest radiator, driver side) hole.
2. I believe I did the TDC check correct, but will make time to re-do.
3. I guess my biggest issue was wasting x dollars on a rebuild of the damper to get it back to factory specs and now having to redraw timing marks on the damper anyway since it doesn't line up as it should.
4. So just to be sure, the damper notch should line up with 0 (on the timing pointer) at TDC, correct?
A harmonic balancer is a two-piece design: an inner hub that keys to the crankshaft and an outer inertia ring, bonded together by a layer of rubber.
When a balancer is rebuilt, the old rubber is burned out, and the two pieces are separated. A new rubber elastomer is injected and cured under pressure to bond them back together. If the outer ring is not placed in the correct orientation relative to the keyway on the inner hub during this process, the timing mark on the balancer will move.
A large error suggests it was re-indexed differently from how it left your car during the rebuild. A lot of engine builders will install their own aftermarket timing pointers for top dead center, so the shop may not have taken special consideration for how the balancer would have come on your car originally.
The balancer on my 80 car is way off, because the rubber between the inner and outer piece has worn out over time, and allowed the outer ring to slip on the inner hub. I learned this fact when I redid my intake gaskets, I went to time the engine with a timing light, and it was useless because of how far the mark on the balencer was off. I ended up dialing in my timing off of vacuum and was successful.
The balancer on my 80 car is way off, because the rubber between the inner and outer piece has worn out over time, and allowed the outer ring to slip on the inner hub. I learned this fact when I redid my intake gaskets, I went to time the engine with a timing light, and it was useless because of how far the mark on the balencer was off. I ended up dialing in my timing off of vacuum and was successful.
You would be wise to change that balancer. If the rubber has deteriorated to the point of the outer ring slipping, what's to keep it from deteriorating further and grenading your engine compartment? I seem to recall a few photos on the C2 or C3 forums showing what happened when an owner experienced an unplanned balancer disassembly; the damage was pretty severe.
not all elastomer dampers have injected rubber. some have rubber that's vulcanized before it's packed/pressed into the gap (not actually bonded). Others have liquid rubber injected into gap and then vulcanized (it's bonded). For example: Pioneer's standard grade has packed/pressed method; while their HD and performance grades are injected & then vulcanized. You can call em and they'll probably say same thing they told me. Give it a whirl; call em. FWIW, I scribe an reference line on new dampers from center thru hub and across rubber and thru outer inertia ring; providing a simple & reliable double-check of any slippage.
You would be wise to change that balancer. If the rubber has deteriorated to the point of the outer ring slipping, what's to keep it from deteriorating further and grenading your engine compartment? I seem to recall a few photos on the C2 or C3 forums showing what happened when an owner experienced an unplanned balancer disassembly; the damage was pretty severe.
An entire engine rebuild is in the works. At this point in time I am fixing leaks, rust, and cosmetic issues. Then Carb, Trans, Engine. Thank you for pointing this out to me though, it wasn't somthing I had given a significant amount of thought.
An entire engine rebuild is in the works. At this point in time I am fixing leaks, rust, and cosmetic issues. Then Carb, Trans, Engine. Thank you for pointing this out to me though, it wasn't somthing I had given a significant amount of thought.
Most elastomeric dampers' hubs and outer inertia rings are made of cast iron; relatively brittle. All that's fine and dandy until the rubber becomes loose and/or unbonded. It's then that the ring begins to bounce around and that cracks and breaks ring. Petrochemicals are enemies of that rubber; keep oil, gas, ps fluid, and engine cleaners away. Don't let spills/leaks lay on it. Timing cover seals leak and are probably most common root cause of rubber failure.
BHJ Dynamics ($$$) has been making best quality elastomeric dampers in USA for decades. Available in every size /configuration imaginable. Billet Steel, billet Aluminum too. Many are SFI. BHJ also manufactures some very good shop tooling; have their damper install tool. All USA. Priced accordingly.
Also, BHJ has published white paper studies on torsional vibration; free & worth the read for those who desire.
